CID 6352

DescriptionCalcium carbide (molecule formula: CaC2), is a kind of important chemical raw materials produced from the chemical processing of limestone. In 1892, H. Maysan (French) and H. Wilson (United state) simultaneously developed a calcium carbide production approach based on furnace Reduction. The United State had successfully achieved industrial production in 1895. The property of calcium carbide is related to its purity. Its industrial product is mostly the mixture of calcium carbide and calcium oxide, and also contains trace amounts of sulfur, phosphorus, nitrogen and other impurities. With the increasing content of impurities, it color exhibits gray, brown to black. The melting point and electrical conductivity both decrease with the decrease of the purity. The purity of its industrial product is usually 80% with m.p. being 1800~2000 °C. At room temperature, it does not react with air, but it can have oxidation reaction at above 350 ℃, and have reaction with nitrogen at 600~700 ℃ to generate calcium cyanamide. Calcium carbide, when coming across with water or steam, generates acetylene and release a large amount of heating. CaC2 + 2H2O─ → C2H2 + Ca (OH) 2 + 125185.32J, 1kg of pure calcium carbide can produce 366 L of acetylene 366l (15 ℃, 0.1MPa). Thereby, for its storage: calcium carbide should be strictly kept away from water. It is usually packed in a sealed iron container, and sometimes stored in a dry warehouse being filled with nitrogen if necessary.

Uses▼ ▲ Industry Applications Benefit Chemical manufacture Production of acetylene gas Raw materials,CaC2 + 2 H2O → C2H2 + Ca(OH)2 Production of calcium cyanamide Raw materials, CaC2 + N2 → CaCN2 + C Production of various acetylene derivatives Source of acetylene gas Production of calcium hydroxide Raw materials, CaC2 + 2 H2O → C2H2 + Ca(OH)2 Steel production The desulfurisation of iron (pig iron, cast iron and steel) Desulfurization agent As a fuel in steelmaking Extend the scrap ratio to liquid iron Ladle treatment facilities A powerful deoxidizer Mining, automobiles and street lighting Carbide lamps React with water to make acetylene gas, which can burn to glow Fruit Artificial ripening fruit Source of acetylene gas Signal flares Floating, self-igniting naval signal flares Used together with calcium phosphide Cylinder gas Metal fabrication and construction Source of acetylene gas Experiment teaching Teaching reagent Experiment reagent

DescriptionCalcium carbide,is a binary salt. It is a grayish-black hard solid that reacts with water to produce acetylene gas, a solid corrosive that is calcium hydroxide, and release heat. Acetylene gas is manufactured by reacting calcium carbide with water. Because acetylene is so unstable, it is not shipped in bulk quantities. Calcium carbide is shipped to acetylene-generating plants where it is reacted with water in a controlled reaction. After the reaction process, the acetylene gas is placed into specially designed containers with a honeycombed mesh inside for shipment and use. It is dissolved in acetone for stability. Calcium carbide has a specific gravity of 2.22, which is heavier than water. The four-digit UN identification number for calcium carbide is 1402. The NFPA 704 designation is health 3, flammability 3, and reactivity 2. The white section at the bottom of the diamond contains a W with a slash through it, indicating water reactivity. It is shipped in metal cans, drums, and specially designed covered bins on railcars and trucks. When shipped and stored, it should be kept in a cool, dry place. Primary uses are in the generation of acetylene gas for welding, vinyl acetate monomer, and as a reducing agent.

UsesCalcium carbide (CaC2) has a garlic-like odor and reacts with water to form acetylene gas plus calcium hydroxide and heat. In the past, it was used in miners’ lamps to continuously produce a small acetylene flame to provide some illumination in coal mines.

UsesCalcium carbide is used as a desulfurizer, dehydrant of steel, fuel in steel making, powerful deoxidizer and as a source of acetylene gas. It is used as a starting material for the preparation of calcium cyanamide, ethylene, chloroprene rubber, acetic acid, dicyandiamide and cyanide acetate. It is used in carbide lamps, toy cannons such as the big-bang cannon and bamboo cannon. It is associated with calcium phosphide and used in floating, self-igniting naval signal flares. Further, it is involved in the reduction of copper sulfide to metallic copper.

UsesCalcium carbide is the most relevant carbide industrially because of its important role as the basis of acetylene industry. In locations where there is shortage of petroleum, Calcium Carbide is used as the starting material for the production of acetylene (1 kg of carbide yields ~300 liters acetylene), which, in turn, can be used as a building block for a range of organic chemicals (e.g. vinyl acetate, acetaldehyde and acetic acid). In some locations, acetylene is also used to produce vinyl chloride, the raw material for the production of PVC. A less important use of Calcium Carbide is related to the ferilizers industry. It reacts with nitrogen to form calcium cyanamide, which is the starting material for the production of cyanamide (CH2N2). Cyanamide is a common agricultural product used to stimulate early foliation. Calcium Carbide can also be employed as desulfurizing agent for producing low-sulfur carbon steel. Also, it is used as a reducing agent to produce metals from their salts, e.g., for direct reduction of copper sulfide to metallic copper.

General DescriptionGrayish-black irregular lump solid. Used to make acetylene and in steel manufacture.

PreparationCalcium carbide (CaC2) is manufactured by heating a lime and carbon mixture to 2000 to 2100°C (3632 to 3812°F) in an electric arc furnace. At those temperatures, the lime is reduced by carbon to calcium carbide and carbon monoxide (CO), according to the following reaction: CaO + 3C → CaC2 + CO Lime for the reaction is usually made by calcining limestone in a kiln at the plant site. The sources of carbon for the reaction are petroleum coke, metallurgical coke, and anthracite coal. Because impurities in the furnace charge remain in the calcium carbide product, the lime should contain no more than 0.5 percent each of magnesium oxide, aluminum oxide, and iron oxide, and 0.004 percent phosphorus. Also, the coke charge should be low in ash and sulfur. Analyses indicate that 0.2 to 1.0 percent ash and 5 to 6 percent sulfur are typical in petroleum coke. About 991 kilograms (kg) (2,185 pounds [lb]) of lime, 683 kg (1,506 lb) of coke, and 17 to 20 kg (37 to 44 lb) of electrode paste are required to produce 1 megagram (Mg) (2,205 lb) of calcium carbide.